*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
^Extrasensory is useless on Roserade.
And always ALWAYS use the Natural Cure ability.
-Don't use Poison Jab when Sludge Bomb is way better. Poison Jab is physical while Sludge Bomb is special. Roserade's physical Attack stat isn't as good as its much higher Special Attack. Always pay attention to the category of an attack to see whether it's physical (orange square) or special (purple square).
-Magical Leaf may have served you well early in the game, but it's really quite weak and there are much stronger grass moves later in the game which you have access to (i.e. Leaf Storm, Energy Ball). Don't keep weak moves on your Pokemon for too long when you come across moves of the same type that are better and stronger.
Now for the sets:
Roserade @Heat Rock/Damp Rock
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature
Trait: Natural Cure
-Sunny Day/Rain Dance
-Energy Ball
-Sleep Powder/Hidden Power [Ice]
-Weather Ball
It can change the weather to its liking. The advantage of sun is that Weather Ball becomes Fire type, hitting Steels supereffectively. The advantage of rain is that it cuts Fire moves and lets Weather Ball turn to Water, hitting Fire types. HP Ice hits Dragons who would be resistant to both types.
Roserade @Choice Specs
EVs: 4 HP / 252 SAtk / 252 Spd
Modest/Timid Nature
Trait: Natural Cure
-Leaf Storm
-Sludge Bomb
-Shadow Ball
-Weather Ball/Hidden Power [Fire/Ice]
It can do incredible amounts of damage with Leaf Storm thanks to its high Sp. Attack and Choice Specs. Sludge Bomb gives it a second STAB move. Shadow Ball hits Ghosts and HP Fire/Ice is for Grass resists (Steel/Dragon mainly). But Weather Ball is also an alternative if the arena is affected by a certain weather effect.
*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
